Radiation detector and imaging system

ABSTRACT

The invention relates to a radiation detector ( 100; 101; 102; 103; 104; 105; 106 ), having a scintillator ( 120 ) for generating electromagnetic radiation ( 202 ) in response to the action of incident radiation ( 200 ). The scintillator ( 120 ) has two opposing end faces ( 121; 122 ) and a lateral wall ( 123 ) between the end faces ( 121; 122 ). The radiation detector has, in addition, a photocathode section ( 130 ) that is located on the lateral wall ( 123 ) of the scintillator ( 120 ) and that generates electrons ( 204 ) in response to the action of electromagnetic radiation ( 202 ) that is generated by the scintillator ( 120 ), a microchannel plate ( 161; 162 ) comprising a plurality of channels ( 165 ), for multiplying the electrons ( 204 ) that have been generated by the photocathode section ( 130 ) and a detection system ( 171; 172 ) for detecting the electrons ( 204 ) that have been multiplied by means of the microchannel plate ( 161; 162 ). The invention also relates to an imaging system ( 110 ) comprising a radiation detector of this type ( 100; 101; 102; 103; 104; 105; 106 ).

The present invention relates to a radiation detector which can be used to detect electromagnetic radiation, in particular X-ray or gamma radiation. The invention furthermore relates to an imaging system, comprising such a radiation detector.

Imaging systems appertaining to medical technology are becoming increasingly important nowadays. Systems of this type are used to generate two- or three-dimensional image data of organs and structures of the human body, which can be used for example for diagnosing causes of illness, for carrying out operations and for preparing therapeutic measures. The image data can be generated on the basis of measurement signals obtained with the aid of a radiation detector.

This is the case for example in X-ray and computed tomography systems (CT). In systems of this type, the body or a body section of a patient to be examined is radiographed by means of X-ray radiation generated by a radiation source. The non-absorbed, transmitted portion of radiation is detected by a detector.

A further example is image generation with the aid of radionuclides, such as is used in positron emission tomography systems (PET) and single photon emission computer tomography systems (SPECT). In this case, the patient to be examined is injected with a radiopharmaceutical which generates gamma quanta either directly (SPECT) or indirectly (PET) through emission of positrons. The gamma radiation is detected by a corresponding radiation detector.

Detectors which can be used for the energy-resolved detection or “counting” of radiation quanta can operate according to different measurement principles. Radiation can be detected either directly, i.e. by direct conversion of the radiation energy into electrical energy, or indirectly. In the case of the last-mentioned variant, use is generally made of a so-called scintillator, which is excited in response to the action of radiation to be detected and reemits the excitation energy by emitting lower-energy electromagnetic radiation. Only the radiation emitted by the scintillator is converted into electrical measurement signals in this case. Detectors of planar construction (so-called “flat detectors”) which are used in the medical field and operate in accordance with these measurement principles are described for example in M. Spahn, “Flat detectors and their clinical applications”, Eur Radiol (2005), 15: 1934-1947.

The conversion of the radiation emerging from a scintillator into an electrical signal can be effected in various ways. Besides use of a photomultiplier provided with a photocathode in the form of an evacuated electron tube, one concept that is common at the present time consists in using a so-called silicon photomultiplier (“SiPM”). This involves a matrix arrangement of avalanche photodiodes (APD) embodied on a shared substrate, electrons being generated in said photodiodes as a result of incident photons, and said electrons being multiplied in an avalanche-like manner.

One disadvantage of silicon photomultipliers, however, is that only part of the total area available for irradiation can be utilized as sensitive or “active” area. The reason for this is that between the active or radiation-sensitive regions there are also insensitive regions, in which resistors and signal lines or wiring structures are arranged. A silicon photomultiplier therefore has a relatively small ratio of active area to (irradiated) total area, said ratio also being designated as “filling factor”. Further disadvantages include noise that occurs during operation, and a relatively high dark rate or dark count, that is to say that signal generation takes place even without irradiation.

A detector comprising a scintillator and a silicon photomultiplier is usually embodied in such a way that the silicon photomultiplier is opposite an end face or rear side of the scintillator. An opposite end face or front side of the scintillator faces the radiation to be detected. As a result, the silicon photomultiplier can detect only that portion of the radiation converted in the scintillator which emerges at the rear side thereof. Proceeding from the respective excitation or interaction location in the scintillator, however, the scintillation radiation is emitted not only in the direction of the rear side, but also in other directions. Furthermore, the radiation is subject to loss processes such as reflection, absorption and scattering. Particularly in the case of scintillators having a high aspect ratio, i.e. a high ratio of height to width, as may be the case for example in a PET system, the losses are therefore relatively high. In the case of an aspect ratio of greater than 7:1, the radiation emerging from a scintillator may make up a proportion of merely 40-60% of the total radiation generated. Although a higher intensity of the incident radiation can be provided in order to compensate for the losses, as a result a patient is also exposed to an increased radiation dose.

It is furthermore disadvantageous that an interaction location of incident radiation in the scintillator cannot be detected or can be detected only with very great difficulty on the basis of the radiation emerging at the rear side of the scintillator. Moreover, it is not possible to obtain information about the height or depth of an interaction in the scintillator. Such disadvantages therefore restrict the resolution of an imaging system provided with such a detector construction.

For image intensification and for electron multiplication, it is furthermore known to use so-called microchannel plates (MCP) having a multiplicity of channels. During operation, an electrical voltage present along the channels is generated, whereby entering electrons can be accelerated within the channels and multiplied by impacts with the channel walls. Use of a microchannel plate in connection with an image intensifier is described in US 2009/0256063 A1, for example.

The object of the present invention is to specify a solution for improved radiation detection in the medical field.

This object is achieved by means of a radiation detector as claimed in claim 1 and by means of an imaging system as claimed in claim 12. Further advantageous embodiments of the invention are specified in the dependent claims.

The invention proposes a radiation detector comprising a scintillator for generating electromagnetic radiation in response to the action of incident radiation. The scintillator has two mutually opposite end faces and a lateral wall between the end faces. The radiation detector furthermore comprises a photocathode section arranged on the lateral wall of the scintillator and serving for generating electrons in response to the action of the electromagnetic radiation generated by the scintillator, a microchannel plate having a plurality of channels for multiplying the electrons generated by the photocathode section, and a detection device for detecting the electrons multiplied by the microchannel plate.

During the operation of the radiation detector, with one of the end faces the scintillator can face the radiation to be detected (in particular X-ray or gamma radiation). The electromagnetic radiation (for example visible or ultraviolet light) generated by the incident radiation in the scintillator and passing to the lateral wall thereof can be taken up or absorbed directly by the photocathode section arranged at this location, and can thus be converted directly and rapidly into electrons. The lateral wall can have a relatively large surface area in comparison with the end faces of the scintillator, as a result of which a large part of the radiation converted in the scintillator can be utilized for generating electrons. This holds true particularly in the case of one possible configuration of the scintillator having a high aspect ratio. On account of these properties, the radiation detector can be distinguished by a high temporal resolution and high efficiency.

It is furthermore advantageous that the radiation detector can have (significantly) less noise and a lower dark rate compared with a conventional detector comprising a silicon photomultiplier. This can be attributed to the fact that without radiation of the scintillator no electrons are generated by the photocathode section and, consequently, (substantially) no electron multiplication takes place in the microchannel plate. Moreover, the microchannel plate used for electron multiplication can be embodied with a high porosity, as a result of which the microchannel plate has a high filling factor (ratio of active area to irradiated total area), which can be (significantly) higher than in the case of a conventional silicon photomultiplier. This likewise fosters a high efficiency of the radiation detector.

In one preferred embodiment, the scintillator is embodied in a parallelepipedal fashion and has four lateral walls between the end faces. A photocathode section for generating electrons is arranged on each of the four lateral walls. As a result, a significant part of the electromagnetic radiation generated in the scintillator can be converted into electrons, which is furthermore advantageous for a high efficiency of the radiation detector.

This correspondingly applies to a further preferred embodiment, according to which a further photocathode section for generating electrons is arranged on an end face of the scintillator.

In a further preferred embodiment, the radiation detector furthermore comprises an electrode arrangement for bringing about a movement of generated electrons to the microchannel plate. As a result, the electrons generated by the photocathode section(s) can be moved or accelerated reliably in the direction of the microchannel plate.

The electrode arrangement preferably comprises a first electrode, which is arranged in the region of an end face of the scintillator, and a second electrode, which is arranged on the microchannel plate. As a result, the radiation detector can have a relatively compact construction.

The second electrode is preferably embodied in the form of a structured layer and has openings via which channels of the microchannel plate are exposed. In this configuration, the electrons emitted by the photocathode section(s) can be accelerated to the second electrode and impinge on the latter with further electrons being liberated. Via the openings in the second electrode, the electrons can enter into the channels of the microchannel plate and be multiplied further here.

In a further preferred embodiment, the microchannel plate is designed for multiplying electrons generated by means of different photocathode sections. For this purpose, the microchannel plate can in particular be arranged in the region of an end face of the scintillator and be provided with larger lateral dimensions than the scintillator. In this way, electrons coming from different photocathode sections can pass to channels in different regions or segments of the microchannel plate, and can be multiplied here.

In a further preferred embodiment, the detection device is designed for separately detecting electrons generated and multiplied by means of different photocathode sections. This affords the possibility of accurately detecting the lateral location of an interaction of a radiation quantum interacting with the scintillator. For this purpose, the detection device can in particular be subdivided into different regions or segments, wherein one or a plurality of trapping electrodes are arranged in each segment.

In a further preferred embodiment, the scintillator, the microchannel plate and the detection device are arranged one above another. As a result, (likewise) a compact detector construction having small lateral dimensions can be made possible.

In a further preferred embodiment, the radiation detector comprises a first and a second photocathode section arranged (in each case) on a lateral wall of the scintillator and serving for generating electrons, and a first and a second microchannel plate for multiplying electrons. Provision is furthermore made of an electrode arrangement designed to bring about a movement of electrons generated by means of the first photocathode section to the first microchannel plate and electrons generated by means of the second photocathode section to the second microchannel plate. Furthermore, the radiation detector comprises a first detection device for detecting electrons multiplied by the first microchannel plate, and a second detection device for detecting electrons multiplied by the second microchannel plate. This configuration of the radiation detector affords the possibility of detecting the height or depth of an interaction in the scintillator. With regard to a parallelepipedal configuration of the scintillator having four lateral walls, for example two of the photocathode sections (angularly) adjoining one another can constitute a first photocathode section, and the other two photocathode sections (angularly) adjoining one another can constitute a second photocathode section.

In a further preferred embodiment, the radiation detector comprises a number of a plurality of scintillators which are arranged alongside one another and on the lateral walls of which are arranged photocathode sections for generating electrons. Provision is furthermore made of a microchannel plate for multiplying electrons generated by means of photocathode sections of the plurality of scintillators, and a detection device for detecting electrons multiplied by the microchannel plate. Such a modular configuration in which the microchannel plate and the detection device are assigned to the plurality of scintillators can be realized relatively cost-effectively, if appropriate.

Such a modular configuration also affords the possibility, with a corresponding electrode arrangement, of bringing about different movements of electrons emitted at lateral walls of the plurality of scintillators, and of assigning a first and second microchannel plate and a first and second detection device to the scintillators in a manner comparable to the embodiment described above.

The invention furthermore proposes an imaging system which comprises a radiation detector in accordance with one of the embodiments described above, and in which, therefore, the advantages described above can likewise be manifested. Such an imaging system can be, for example, an X-ray or computed tomography system or else a positron emission tomography or single photon emission computed tomography system. With regard to such imaging systems, provision can be made for the above-described detector construction or one of the above-described embodiments to constitute in each case an individual detector element or a “pixel” of an associated detector, and for a multiplicity of such detector elements or “pixels” to be arranged alongside one another in particular in a planar fashion and/or in a circular or partly circular fashion.

The above-described properties, features and advantages of this invention and the way in which they are achieved will become clearer and more clearly understood in association with the following description of exemplary embodiments which are explained in greater detail in association with the drawings, in which:

FIG. 1 shows a schematic illustration of an X-ray system;

FIG. 2 shows a schematic perspective illustration of constituent parts of a detector element comprising photocathode sections on lateral walls of a scintillator, with an elucidation of the functioning thereof;

FIG. 3 shows a schematic perspective illustration of a further detector element constructed in accordance with the components from FIG. 2;

FIG. 4 shows a schematic lateral illustration of an enlarged excerpt from the detector element from FIG. 3;

FIG. 5 shows a schematic perspective illustration of a further detector element, designed for segment-by-segment detection of electrons, wherein the electrons are generated by different photocathode sections;

FIG. 6 shows a schematic plan view of an electrode arrangement of a detection device used in the detector element from FIG. 5;

FIG. 7 shows a schematic perspective illustration of components of a further detector element, designed to move electrons generated by different photocathode sections in different directions;

FIG. 8 shows a schematic plan view of an electrode arrangement used in the detector element from FIG. 7 for bringing about the different electron movements;

FIG. 9 shows a schematic perspective illustration of the detector element constructed in accordance with the components of FIGS. 7 and 8;

FIG. 10 shows a schematic perspective illustration of a further detector element comprising a plurality of scintillators arranged alongside one another;

FIG. 11 shows a schematic lateral illustration of the plurality of scintillators of the detector element from FIG. 10; and

FIG. 12 shows a schematic perspective illustration of a further detector element comprising a plurality of scintillators arranged alongside one another, wherein the detector element is designed to bring about electron movements in different directions.

Embodiments of a detector or detector element which can be used to detect electromagnetic radiation, in particular high-energy radiation such as X-ray or gamma radiation, are described with reference to the following figures. In order to produce the embodiments described, method processes known from the field of semiconductor and detector technology can be carried out and customary materials can be used, and so they will be discussed only in part.

The detector concept described here is provided for use in association with imaging systems appertaining to medical technology. In systems of this type, two- or three-dimensional image data of organs and structures of the human body are generated on the basis of measurement signals obtained with the aid of a corresponding radiation detector.

For exemplary elucidation, FIG. 1 illustrates an X-ray system 110 which can be used for diagnostic and interventional imaging. The X-ray system 110 comprises a radiation source 111 for emitting X-ray radiation (“X-ray emitter”) and an associated detector 100 of planar construction (“flat detector”) for detecting the radiation. Radiation source 111 and detector 100 are arranged opposite one another at the ends of a C-shaped holding device 112. On account of this configuration, this arrangement is also designated as “C-arc” or “C-arm”.

A patient to be examined is situated on a patient supporting couch 117 and in this case is arranged between radiation source 111 and detector 100. During the operation of the X-ray system 110, the body or a body section of the patient is radiographed with the X-ray radiation generated by the radiation source 111, and the non-absorbed, transmitted portion of radiation is detected by means of the detector 100.

The holding device 112 is furthermore fixed to a robot 113 provided with a plurality of axes and/or articulations, with the aid of which robot the radiation source 111 and the detector 100 can be brought to a desired position in relation to the patient. For controlling the X-ray system 110 and for processing and/or evaluating measurement signals of the detector 100, in particular for generating the desired image data, the X-ray system 110 furthermore comprises a control and/or evaluation device 114. The latter is connected to a corresponding display device or a display, as is indicated in FIG. 1.

Alongside the X-ray system 110 from FIG. 1, the detector concept described below can also be used in association with other imaging systems (not illustrated). By way of example, systems comprising a gantry, such as a computed tomography system (CT), for example, are appropriate. Such a system can comprise an annular or circular-cylindrical detector and a rotatable X-ray source. Further exemplary applications with a gantry include positron emission tomography systems (PET) and single photon emission computed tomography systems (SPECT). In this case, the patient to be examined is injected with a radiopharmaceutical which generates gamma quanta either directly (SPECT) or indirectly (PET) through emission of positrons. Said quanta can be detected likewise by an annular or circular-cylindrical detector.

FIG. 2 shows a schematic perspective illustration of a basic construction of a detector element 101 which can be used for detecting incident high-energy radiation. The embodiments of detector elements described further below with reference to the other figures are constructed on the basis of the detector principle shown here, and so the aspects described below can also apply to these embodiments. Furthermore, it is pointed out that a radiation detector of an imaging system, for example the detector 100 of the system 110 from FIG. 1, can comprise a multiplicity of detector elements constructed in this way, wherein said detector elements can be arranged alongside one another in the form of “pixels” in a matrix-like manner. In this case, in particular, planar, but also annular or partly annular arrangements can be present. The image data respectively desired can be generated on the basis of the measurement signals generated by the individual pixels or detector elements of a detector.

As is illustrated in FIG. 2, the detector element 101 comprises a scintillator 120, which serves to convert the high-energy radiation to be detected into a low(er)-energy radiation. The scintillator 120 is embodied in a parallelepipedal fashion and has two mutually opposite end faces 121, 122 and four lateral walls 123 between the two end faces 121, 122, said lateral walls adjoining one another at a right angle. The end face 122 directed toward the top in FIG. 2 is also designated hereinafter as “front side” and the end face 121 directed toward the bottom as “rear side” of the scintillator 120. Front and rear sides 122, 121 are connected to one another via the lateral walls 123 at the periphery or edge.

As is furthermore indicated in FIG. 2, the scintillator 120 has a high aspect ratio, i.e. a high ratio of height (distance between the end faces 121, 122) to width (lateral dimension or distance between two mutually opposite lateral walls 123), which is greater or significantly greater than one. In this way, it is possible to obtain a high absorption of the high-energy radiation to be detected, which is indicated on the basis of a radiation quantum 200 in FIG. 2, in the scintillator 120. In this connection it is pointed out that the components illustrated in FIG. 2, but also in the other figures, and their dimensions may be illustrated in a manner not true to scale. By way of example, it is possible for the scintillator 120 to have a larger height or a larger aspect ratio.

During the operation of the detector element 101, the front side 122 of the scintillator 120 faces the radiation to be detected, such that the radiation can be incident or coupled into the scintillator 120 via the front side 122. A radiation quantum 200 (in particular X-ray quantum or gamma quantum) of the incident radiation can bring about an excitation locally upon passing through the scintillator 120. The excitation energy deposited or absorbed during this process is reemitted by the scintillator 120 in the form of lower-energy radiation quanta or photons 202. In this case, the number of emitted photons 202 may be proportional to the original energy of the radiation quantum 200 that interacts with the scintillator material. The scintillation mechanism which takes place in this case will not be discussed in more specific detail. The scintillation radiation generated by the scintillator 120 may be visible or ultraviolet light, in particular.

Alongside radiation emission in the direction of the end faces 121, 122 of the scintillator 120, a large part of the scintillation radiation or photons 202 generated in the scintillator 120 is emitted in the direction of the lateral walls 123. This is the case, in particular, if the scintillator 120, as in the present case, has a high aspect ratio, and, consequently, the lateral walls 123 have a relatively large surface area in comparison with the end faces 121, 122 of the scintillator 120. In the case of the detector element 101, provision is made for utilizing in particular this significant portion of radiation at the lateral walls 123 for detecting radiation, as a result of which a high efficiency can be achieved.

The detector element 101 comprises for this purpose a respective photocathode section 130 on all four lateral walls 123, by means of which photocathode sections photons 202 emitted to the lateral walls 123 and emerging at the lateral walls 123 can be converted into electrons 204 (photoelectrons) with use being made of the photoelectric effect. For each photon 202 which impinges on a photocathode section 130 and is absorbed here, the relevant photocathode section 130 can emit an electron 204.

For reasons of clarity, only three photocathode sections 130 provided on lateral walls 123 are illustrated in FIG. 2. Said sections are furthermore provided with the reference signs 130 a, 130 b and 130 c for differentiation, these reference signs in part also being used in the other figures. In this case, the addition “a” refers to the section 130 arranged on the left, the addition “b” refers to the section 130 offset toward the rear with respect to the plane of the drawing, and the addition “c” refers to the section 130 arranged on the right. In the other figures, by contrast, the designation “d” is provided for a fourth photocathode section 130, which is not shown in FIG. 2 and which is arranged at the front in the plane of the drawing.

Each of the photocathode sections 130—in a departure from the spaced-apart illustration of FIG. 2—is arranged directly on a respective lateral wall 123 of the scintillator 120. The layer-type photocathode sections 130 preferably have substantially the same surface area as the relevant lateral walls 123, such that all lateral walls 123 are substantially completely covered by the photocathode sections 130. In this case, the photocathode sections 130 can be present in the form of a continuous layer (peripherally) enclosing the scintillator 120.

The photocathode sections 130 constitute semitransparent photocathodes or transmission photocathodes which operate transmissively. In this case, the photocathode sections 130 are irradiated at the side facing the scintillator 120 or bearing on the lateral walls 123 thereof, and electrons 204 are emitted at an opposite side of the photocathode sections 130 with respect thereto. This is elucidated in FIG. 2 with the aid of the right-hand photocathode section 130 c. The direct arrangement of the photocathode sections 130 on the lateral walls 123 of the scintillator 120 likewise contributes to the high efficiency of the detector element 101. What can be achieved in this configuration is that the scintillation radiation passing to the lateral walls 123 and emerging at the lateral walls 123 is directly taken up or absorbed by the photocathode sections 130 and converted into electrons 204. Radiation reflection and the situation where the radiation is “reflected back and forth” in the scintillator 120, associated with corresponding loss processes, can (largely) be avoided in this case. To put it another way, the first “contact” of a photon 202 with a lateral wall 123 can lead to the generation of an electron 204.

The configuration of the scintillator 120 with the photocathode sections 130 on the lateral walls 123 thus affords the possibility of obtaining rapid access to a large number of scintillation photons 202 by an extremely short route. In this way, the detector element 101 can have a high efficiency and a high temporal resolution. These advantages correspondingly also hold true for a detector constructed from a plurality of such detector elements 101, and thus for an associated imaging system. This affords the possibility, in particular, of exposing a patient to be examined only to a low radiation dose. Alongside the scintillator 120 and the photocathodes 130 arranged thereon, the detector element 101 furthermore comprises an arrangement composed of two electrodes 140, 150, a microchannel plate 161 having a multiplicity of microchannels, and a detection device 171. With the aid of the two electrodes 140, 150, an electric field E is generated in order to bring about a movement of the electrons 204 generated photoelectrically at the lateral walls 123 of the scintillator 120 to the microchannel plate 161. This is likewise elucidated in FIG. 2 only with the aid of the right-hand lateral wall 123 provided with the photocathode section 130 c. In this case, the electrode 140 can constitute a cathode, and the other electrode 150 an associated anode or dynode, on which the electrons 204 can impinge with further electrons 204 being liberated. The electrodes 140, 150 are furthermore preferably embodied and positioned with respect to one another in such a way that the direction of the electric field E runs parallel to the longitudinal axis of the scintillator 120.

In order that the electrons 204 can pass to the microchannel plate 161 arranged below the electrode 150, the electrode 150 can be provided with corresponding openings (not illustrated in FIG. 2). Moreover, provision is preferably made for the electrode 150 (in a departure from the illustration of FIG. 2) to be arranged directly on the microchannel plate 161. The electrons 204 passing to the microchannel plate 161 can be rapidly multiplied in the channels thereof and subsequently trapped and detected with the aid of the detection device 171 arranged below the microchannel plate 161, or with the aid of one or more readout electrodes (“readout pad”) provided here and serving as anodes. A corresponding output signal can be generated on the basis of this. The detection device 171 can (in a departure from the illustration in FIG. 2) be directly connected to the microchannel plate 161. These and further possible details concerning the components 140, 150, 161, 171 and the functioning thereof will be discussed even more thoroughly in connection with FIGS. 3 and 4.

The above-described functioning of the detector element 101 requires the presence of an evacuated atmosphere or a vacuum (at least) in that region in which free electrons 204 are present, i.e. starting from the generation at the lateral walls 123 of the scintillator 120 with the photocathode sections 130 through to detection with the aid of the detection device 170. In FIG. 2, and also in the further figures, the presence of such an evacuated environment or a vacuum 190 is indicated with the aid of broken lines. The provision of the evacuated environment 190 can be made possible in particular with a corresponding housing (not illustrated).

FIG. 3 shows a schematic perspective illustration of a detector element 102 constructed from the constituent parts described above. FIG. 4 shows a schematic lateral illustration of an enlarged excerpt from the detector element 102, on the basis of which further possible details of the detector element 102 become clear. As is illustrated in FIG. 3, the electrode 140, the scintillator 120 coated with the photocathodes 130, the other electrode 150, the microchannel plate 161 and the detection device 171 are arranged one above another with respect to one another in the case of the detector element 102. In this way, the detector element 102 can have a relatively compact construction with small lateral dimensions.

The electrode 140, which can be embodied in the form of a rectangular or square plate, is arranged in the region of the front side 122 or on the front side 122 of the parallelepipedal scintillator 120. The other electrode 150, as shown in FIG. 4, is embodied in the form of a structured layer arranged on a side of the microchannel plate 161 situated opposite the rear side 121 of the scintillator 120. This side of the microchannel plate 161 is also designated hereinafter as the “front side” of the microchannel plate 161. Both electrodes 140, 150 extend (substantially) parallel to one another, as illustrated in FIG. 3, and project laterally beyond the lateral walls 123 of the scintillator 120 (or planes predefined by the lateral walls 123). The two electrodes 140, 150 can have the same or comparable external dimensions.

As a result of the parallel arrangement of the electrodes 140, 150 and the lateral projection thereof beyond the lateral walls 123 of the scintillator 120, an electric field E generated with the aid of the two electrodes 140, 150 runs (also) laterally with respect to the lateral walls 123 parallel to the longitudinal axis of the scintillator 120. By means of the electric field E, electrons 204 emitted at the lateral walls 123 by the photocathode sections 130 or 130 a, 130 b, 130 c, 130 d in response to the action of the scintillation radiation can be reliably deflected toward the electrode 150 and accelerated in the direction of the electrode 150. For the generation of the electric field E, corresponding electrical potentials coordinated with one another are applied to the two electrodes 140, 150. For this purpose, the detector element 102 comprises a suitable connection structure (not illustrated). The potential difference between the electrodes 140, 150 can be in the high-voltage range, in particular.

The microchannel plate 161 arranged on the rear side 121 of the scintillator 120 or situated opposite the rear side 121 has a plate-shaped main body permeated by a multiplicity (for example a few thousand) of microscopically fine channels 165 (see FIG. 4). The channels 165 can be arranged with a close pitch in a pixel-like manner with respect to one another and can be embodied in a manner running parallel to one another. The microchannel plate 161, in a manner comparable with the two electrodes 140, 150, (likewise) has larger lateral dimensions than the scintillator 120 and extends laterally beyond the lateral walls 123 thereof (or planes predefined by the lateral walls 123), as a result of which electrons 204 emitted by the lateral walls 123 can pass to the microchannel plate 161 and be multiplied therein.

The front side of the microchannel plate 161 “coated” with the electrode 150 can be arranged at a distance from the rear side 121 of the scintillator 120, as shown in FIG. 4, (at least) in the region illustrated here. In a departure from this, provision can be made for scintillator 120 and microchannel plate 161 to directly adjoin one another at one or a plurality of other locations, such that the scintillator 120 is placed on the front side of the microchannel plate 161. For this purpose, the microchannel plate 161 can have at the front side for example one or more projecting supporting structures or spacer structures on which the scintillator 120 can bear (not illustrated). At such supporting locations, no coating of the microchannel plate 161 with the electrode 150 is provided.

With reference to FIG. 4, it furthermore becomes clear that the electrode 150 arranged on the front side of the microchannel plate 161 is embodied in the form of a structured layer and has holes or openings 159. The channels 165 of the microchannel plate 161 are exposed via the openings 159, such that electrons 204 can enter into the channels 165 at the front side of the microchannel plate 161. The microchannel plate 161 is furthermore provided with a structured surface profile at the front side, and has elevations 166 between the channels 165 with a shape or contour decreasing in size, for example trapezoidal or tetrahedral shape. In this way, the electrode 150 arranged here likewise has a correspondingly structured or profiled surface shape having for example trapezoidal or tetrahedral sections tapering in particular obliquely toward one another. This configuration makes it possible that electrons 204 (primary electrons) emitted by the photocathode sections 130 in the direction of the electrode 150 can impinge on the electrode 150 and can eject or liberate further electrons 204 (secondary electrons) here, wherein the electrons 204 can subsequently enter into the channels 165 of the microchannel plate 161 via the openings 159 and can be multiplied further, as indicated in FIG. 4.

For this purpose, during the operation of the detector element 102, (likewise) an electrical (high) voltage is applied between the front side and a rear side of the microchannel plate 161 situated opposite the front side, as a result of which an electric field is present along the channels 165. Electrons 204 entering into a channel 165 at the front side of the microchannel plate 161 are moved or accelerated owing to the electric field in the direction of the rear side of the microchannel plate 161 and thus in the direction of the detection device 171 provided in this region. In this case, the small lateral dimensions of the channels 165 have the effect that the electrons 204 can multiply impact the wall of the relevant channel 165 during this movement. Upon each impact, further electrons 204 can be released or ejected from the channel wall and for their part can likewise be accelerated within the channel 165 and liberate further electrons 204 as a result of impacts with the channel wall. This process continues over the length of the channel 165 and is therefore associated with an avalanche- or cascade-like increase in electrons 204 as illustrated in FIG. 4.

The electrons 204 multiplied in accordance with this process in the channels 165 of the microchannel plate 161 impinge on the detection device 171 at the rear side of the microchannel plate 161 and are detected by said detection device. In this case, the detection device 171 can generate a corresponding electrical output signal (for example voltage drop across a resistor). Such an output signal is dependent on the number or total charge of the electrons 204 collected in the detection device 171, and thus on the excitation energy originally deposited in the scintillator 120.

The detection device 171 can have larger lateral dimensions than the microchannel plate 161, as shown in FIG. 3. Moreover, the detection device 171, as illustrated in FIG. 4, can be connected to the microchannel plate 161 or to the rear side thereof and comprise per channel 165 a respective corresponding electrode 175 for trapping or collecting multiplied electrons 204. Alternatively, it is also possible for the detection device 171 to be provided with larger or wider electrodes which are assigned to a plurality of channels 165. A configuration having an individual or large-area electrode for trapping the electrons 204 multiplied in all the channels 165 of the microchannel plate 161 is also possible.

The presence of an acceleration voltage and thus of an electric field along the channels 165 of the microchannel plate 161 requires the application of corresponding electrical potentials to the front and rear side thereof. At the front side of the microchannel plate 161, this can be effected by means of the electrode 150 arranged here. With regard to the rear side, this can be performed with the aid of the detection device 171 or the electrode(s) 175 thereof.

As is illustrated in the enlarged excerpt illustration in FIG. 4, the detector element 102 comprises, alongside the photocathode sections 130 provided on the lateral walls 123 of the scintillator 120, a further (optional) semitransparent photocathode section 131 arranged on the rear side 121 of the scintillator 120. In this case, all the photocathode sections 130, 131 can be present in the form of a continuous coating of the scintillator 120.

The photocathode section 131 affords the possibility of additionally utilizing a portion of the scintillation radiation generated in the scintillator that passes to the rear side 121 and of directly converting it into photoelectrons 204. By means of the electric field E which is (also) present in this region, is produced with the aid of the electrodes 140, 150 and is oriented parallel to the longitudinal axis of the scintillator 120, the electrons 204 emitted at the rear side 121 can likewise be accelerated in the direction of the electrode 150. This can be followed once again by the processes described above, i.e. impingement of the electrons 204 on the electrode 150 with liberation of further electrons 204, entry of the electrons 204 into channels 165 of the microchannel plate 161 and multiplication of said electrons, and detection of the multiplied electrons 204 with the aid of the detection device 171. For further details in this regard, reference is made to the description above. With regard to details pertaining to the photocathode section 131, reference is made to the above explanations concerning the other photocathode sections 130, which apply analogously here.

Alongside the above-described utilization of the scintillation radiation emitted in particular to the lateral walls 123 of the scintillator 120, the use of the microchannel plate 161 used for electron multiplication also contributes to a high detection efficiency. In particular, the detector element 102 (and 101) can have a low noise proportion and a low dark rate. This is owing to the fact that the production of electron avalanches in the channels 165 of the microchannel plate 161 and thus the generation of a corresponding signal in the detection device 171 take place (substantially) only if the scintillator 120 emits radiation and the photocathode sections 130, 131 generate photoelectrons 204 in response to the action of the scintillation radiation. Moreover, the microchannel plate 161 can be embodied with small distances between the microchannels 165, and consequently with a high porosity. This is associated with a high filling factor, which can be (significantly) higher than in the case of a conventional silicon photomultiplier.

Materials known from semiconductor and detector technology can be used for the constituents of the detector element 102 (and 101). By way of example, the electrodes 140, 150 are formed from an electrically conductive or metallic material. The electrode 150 arranged on the microchannel plate 161 preferably comprises a material having high secondary electron emission, as a result of which the impingement of photoelectrons 204 on the electrode 150 can be associated with liberation of a multiplicity of (further) electrons 204 and thus high electron multiplication.

The use of an inorganic material or of a crystal is considered for the scintillator 120. Preferably, this involves a “fast” scintillator 120, in which the scintillation mechanism, i.e. the conversion of the incident high-energy radiation into the lower-energy scintillation radiation, takes place in a short time duration. One material considered for this purpose is CsF or LSO, for example. With regard to a possible size of the scintillator 120, consideration is given, for example, to lateral dimensions or a width in the range of a few 100 μm to a few mm, and a height in the range of a few mm to a few 10 mm. In this case, the scintillator 120 has an aspect ratio of (significantly) greater than one, which can be greater than 7:1, for example, with regard to PET applications.

Materials such as, for example, CsI, CsTe, Cs3Sb, diamond and GaN are appropriate for the photocathode sections 130, 131. The photocathode sections 130, 131 and the scintillator 120 or the materials thereof are in this case coordinated with one another in such a way that the scintillation radiation coming from the scintillator 120 can be converted into free electrons 204 in the photocathode sections 130, 131. Since the photocathode sections 130, 131 operate transmissively, as described above, the photocathode sections 130, 131 are also embodied with a relatively small thickness or layer thickness, for example in the range of a few 10 nm, on the scintillator 120.

The microchannel plate 161 preferably comprises a semiconductor material such as silicon, in particular. In this way, the microchannel plate 161 can be produced in a simple manner, in particular with the aid of a lithographic patterning and etching method. The microchannel plate 161 can furthermore be embodied in such a way that the microchannel plate 161, alongside a basic or starting material, in particular a semiconductor material such as silicon, additionally comprises even further materials or layers (not illustrated). By way of example, a coating having high secondary electron emission can be provided within the channels 165 in order to be able to liberate a multiplicity of further electrons 204 in the event of wall impacts of electrons 204. The microchannel plate 161, which (like the electrodes 140, 150) has larger lateral dimensions than the scintillator 120, can have for example a height (distance between front and rear sides) in the range of a few 100 μm to a few mm. The pores or channels 165 of the microchannel plate 161 can have a width or a diameter of a few μm to a few 10 μm.

With regard to the channels 165, provision can furthermore be made for said channels, contrary to the illustration in FIG. 4, to be arranged in a manner obliquely tilted relative to a normal to a plane predefined by the microchannel plate 161 (or by the front side and/or rear side thereof). In this case, for example, it is possible to provide an angle in a range of 10° between the normal to the plate and a longitudinal axis of the channels 165. What can be achieved as a result is that the electrons 204 multiply impact the channel walls independently of their entrance angles upon entering into the channels 165 and, consequently, can liberate further electrons 204.

A series of different configurations are possible for the detection device 171 as well. The detection device 171, which, as shown in FIG. 3, can have larger lateral dimensions than the microchannel plate 161, can be embodied for example like the microchannel plate 161 in the form of a semiconductor or silicon substrate with one or more electrodes 175 composed of a conductive or metallic material. In this way, a bonding method known from semiconductor technology can be carried out in order to connect these two components 161, 171. Alternatively, the detection device 171 can also be embodied for example in the form of a ceramic carrier provided with one or more electrodes 175.

In a configuration of the detection device 171 having a plurality of electrodes 175, the latter can be present for example in the form of rows and columns or in the form of a matrix arrangement. Alternatively, however, other configurations of electrodes are also possible, for example in the form of crossed striplines or strip-shaped electrodes (“transmission line system”).

The detection device 171 can furthermore also be present in the form of an application specific integrated circuit (ASIC). In this way, the detection device 171 can be designed not only for detecting or reading out a total charge of an electron avalanche and for generating an output signal on the basis thereof, but also for (at least partly) conditioning or evaluating the same.

One possible modification of the detector element 102 in FIGS. 3 and 4 consists in providing photocathode sections 130 for photoelectrically generating electrons 204 only on the lateral walls 123 of the scintillator 120, and omitting the photocathode section 131 arranged on the rear side 121 of the scintillator 120. In this way, the configurations which are described below and are not illustrated can additionally be considered, which can be realized either jointly or (if appropriate) independently of one another. By way of example, the possibility is afforded that, instead of a whole- or large-area coating of the microchannel plate 161 with the electrode 150, the electrode 150 is formed only in a frame-shaped region, i.e. laterally with respect to the lateral walls 123 of the scintillator 120, on the front side of the microchannel plate 161, since photoelectrons 204 are only emitted by the lateral walls 123. A frame-shaped configuration is equally possible for the other electrode 140. Moreover, the microchannel plate 161 can be provided with channels 165 only in a frame-shaped region corresponding to the frame-shaped electrode 150. The same applies to the detection device 171, which can likewise comprise one or a plurality of trapping electrodes 175 only in a frame-shaped region. Furthermore, provision can also be made for the scintillator 120 to be placed directly on the microchannel plate 161 over the entire rear side 121, and therefore (in a departure from FIG. 4) there is no distance between the scintillator 120 and the microchannel plate 161.

Further possible configurations of detector elements are described with reference to the following figures. In this case, it is pointed out that, with regard to already described details relating to aspects and components of identical type or corresponding aspects and components, functioning, usable materials, size dimensions, possible advantages, etc., reference is made to the above explanations.

FIG. 5 shows a schematic perspective illustration of a further detector element 103, which is constructed in a manner comparable with the detector element 102 from FIG. 3. The detector element 103 or the detection device 171 thereof is designed to detect electrons 204 separately from one another, said electrons being generated and subsequently multiplied with the aid of different photocathode sections 130 arranged on lateral walls 123.

In order to elucidate this functioning, FIG. 5 indicates a subdivision of the electrode 150 into trapezoidal electrode regions or segments 150 a, 150 b, 150 c, 150 d which are present laterally with respect to the lateral walls 123 of the scintillator 120. The electrode 150 (in a manner corresponding to FIG. 4) can be formed on the microchannel plate 161 and with openings 159. The individual segments 150 a, 150 b, 150 c, 150 d are assigned to the photocathode sections 130 a, 130 b, 130 c, 130 d arranged on the different lateral walls 123 of the scintillator 120. The shown subdivision of the electrode 150, which can be merely fictitious, is intended to elucidate the fact that the electrons 204 emitted at the different lateral walls 123 can be deflected to the different segments or quadrants 150 a, 150 b, 150 c, 150 d on account of the electric field E generated by the electrodes 140, 150 and situated parallel to the longitudinal axis of the scintillator 120. In this case, electrons 204 are accelerated from the photocathode section 130 a to the segment 150 a, from the photocathode section 130 b to the segment 150 b, from the photocathode section 130 c to the segment 150 c, and from the photocathode section 130 d to the segment 150 d.

In a corresponding manner, the electrons 204 which impinge on the different segments 150 a, 150 b, 150 c, 150 d and are liberated here are multiplied separately from one another or in corresponding (fictitious) segments of the microchannel plate 161. This makes it possible for the multiplied electrons 204 also to be detected separately from one another by the detection device 171 arranged (in a manner corresponding to FIG. 4) on the rear side of the microchannel plate 161.

For this purpose, provision is made for the detection device 171 to have separate electrode regions 176 a, 176 b, 176 c, 176 d, as illustrated with reference to the schematic plan view illustration in FIG. 6. The electrode regions 176 a, 176 b, 176 c, 176 d are assigned to the individual lateral walls 123 of the scintillator 120 or to the photocathode sections 130 a, 130 b, 130 c, 130 d and thus to the “multiplying segments” of the microchannel plate 161 and to the electrode regions 150 a, 150 b, 150 c, 150 d of the electrode 150, and can therefore be embodied in a trapezoidal fashion. Each electrode region 176 a, 176 b, 176 c, 176 d can in each case have a large-area electrode, or else a plurality of electrodes, for example in a manner corresponding to the structure shown in FIG. 4. The electrons 204 generated and multiplied separately from one another can be detected separately via the electrode regions 176 a, 176 b, 176 c, 176 d. Using this as a basis, corresponding output signals can be generated using the charge quantities detected by the individual electrode regions 176 a, 176 b, 176 c, 176 d.

The separate and segment-by-segment detection of electrons 204 generated and multiplied by means of different photocathode sections 130 a, 130 b, 130 c, 130 d affords the possibility of determining, simply and accurately, the lateral location of the interaction (“x/y position”) of a radiation quantum 200 which excites the scintillator 120 in the scintillator 120. In this case, it is possible to make use of the fact that the point in time or the temporal development and/or the magnitude of the charge signals obtained by the electrode regions 176 a, 176 b, 176 c, 176 d are/is dependent on the proximity of the interaction to the respective lateral walls 123. In order to determine the lateral interaction location, it is possible, for example, to form summation and/or difference signals from the individual signals. Particularly in the case of one possible configuration of the detection device 171 in the form of an ASIC circuit, this can be carried out by the detection device 171 itself.

Making it possible to determine a lateral interaction location in a scintillator 120 proves to be expedient for an imaging system in which the associated detector is constructed from a plurality of detector elements 103 constructed in this way. Alongside a high efficiency and a high temporal resolution, the relevant detector can have a high lateral spatial resolution as a result even in the case of relatively large lateral scintillator dimensions. In the case of the detector element 103 as well, in a manner comparable with the detector element 102, an optional photocathode section 131 can be provided on the rear side 121 of the scintillator 120, such that an arrangement as shown in FIG. 4 can be present. In a corresponding manner, the electrons 204 emitted at the rear side 121 can be accelerated to a rectangular region of the electrode 150 enclosed by the segments 150 a, 150 b, 150 c, 150 d, can impinge here with further electrons 204 being liberated, and the electrons 204 can once again be multiplied separately (i.e. separately from the electrons 204 of the other segments 150 a, 150 b, 150 c, 150 d) in the microchannel plate 161. These electrons 204, too, can be detected separately by the detection device 171. For this purpose, the detection device 171 can have an (optional) rectangular electrode region 177 enclosed by the electrode regions 176 a, 176 b, 176 c, 176 d, as is indicated in FIG. 6.

The “central” electrode region 177, like the other electrode regions 176 a, 176 b, 176 c, 176 d, can have a large-area electrode or else a plurality of electrodes for detecting multiplied electrons 204.

In the case of the detector elements 102, 103 described above, the arrangement comprising microchannel plate 161 (with electrode coating 150), and detection device 171 is provided in the region of the rear side 121 of the scintillator 120. Alternatively, however, a configuration of the detector elements 102, 103 that is symmetrical thereto is also possible, wherein the arrangement comprising microchannel plate 161 and detection device 171 is provided in the region of the front side 122 of the scintillator 120. In this configuration, the electrode 140, serving as cathode, is arranged at or on the rear side 121 of the scintillator 120, and an optional photocathode section 131 is arranged on the front side 122 of the scintillator 120. In this case, the high-energy radiation to be detected can be transmitted (without interaction) through the detection device 171, the microchannel plate 161 (including the electrode 150) and the optional photocathode section 131 and can subsequently be incident in the scintillator 120, wherein the processes described above can once again occur.

A further possible variant consists in providing microchannel plates and detection devices on different sides, in particular on the two end faces 121, 122 of the scintillator 120, and bringing about electron movements in different or mutually opposite directions. This affords the possibility of also detecting the height or depth of an interaction in the scintillator 120. One possible configuration will be explained in greater detail with reference to the following figures.

FIG. 7 shows a schematic perspective illustration of constituent parts of a further detector element 104. Alongside the parallelepipedal scintillator 120, on the four lateral walls 123 of which are arranged (once again) respective photocathode sections 130 a, 130 b, 130 c, 130 d for photoelectrically generating electrons 204, the detector element 104 has a mirror-symmetrical electrode arrangement for bringing about different electron movements.

The electrode arrangement comprises two L-shaped electrodes 141, 142 in the region of the front side 122 of the scintillator 120, and two further L-shaped electrodes 151, 152 in the region of the rear side 121 of the scintillator 120. In this case, the two electrodes 141, 142, which project laterally beyond the edge of the front side 122 of the scintillator 120 or are present (at least) in a region laterally with respect to the lateral walls 123, form a frame-shaped structure. In the same way, the other two electrodes 151, 152, which project laterally beyond the edge of the rear side 121 of the scintillator 120 or are present (at least) in a region laterally with respect to the lateral walls 123, likewise form a frame-shaped structure.

Both the electrodes 141, 151 and the electrodes 142, 152 are arranged parallel to one another and one above another. Furthermore, the electrode pair 141, 151 is arranged in the region of the photocathode sections 130 a, 130 d, and the other electrode pair 142, 152 is arranged in the region of the photocathode sections 130 b, 130 c. This relationship is also illustrated in the schematic plan view illustration in FIG. 8.

As is furthermore indicated in FIG. 7, an electric field E in the direction of the bottom electrode 151 can be produced by means of the two electrodes 141, 151 situated opposite one another, wherein the electrode 141 can constitute a cathode, and the other electrode 151 can constitute an anode or dynode. In this way, the electrons 204 generated by means of the photocathode sections 130 a, 130 d can be accelerated downward in the direction of the electrode 151. By contrast, an electric field E in the opposite direction, i.e. in the direction of the top electrode 142, can be produced by means of the other two electrodes 142, 152 situated opposite one another, wherein here the electrode 152 can constitute a cathode, and the other electrode 142 can constitute an anode or dynode. In this way, the electrons 204 emitted by photocathode sections 130 b, 130 c can be accelerated upward in the direction of the electrode 142. The electric fields E generated by the electrode pairs 141, 151 and 142, 152 are once again oriented parallel to the longitudinal axis of the scintillator 120.

FIG. 9 shows a schematic perspective illustration of the detector element 104 having additional constituent parts for detecting the electrons 204 moved in different directions. The detector element 104 comprises a first and second microchannel plate 161, 162 and a first and second detection device 171, 172. These components 161, 162, 171, 172 can be constructed in the manner described above with reference to the detector elements 101, 102.

As is shown in FIG. 9, the first microchannel plate 161 is arranged in the region of the rear side 121 of the scintillator 120 or opposite the rear side 121. Moreover, the two electrodes 151, 152 are arranged on the front side of the microchannel plate 161. In this case, a construction comparable with FIG. 4 can be present, that is to say that the electrodes 151, 152 can comprise a surface profile comparable with the electrode 150 and openings exposing channels of the microchannel plate 161. Furthermore, the scintillator 120 and the microchannel plate 161 can directly adjoin one another, wherein the microchannel plate 161 can comprise, for example, one or more projecting supporting structures. The detection device 171 provided on the rear side of the microchannel plate 161 can be directly connected to the microchannel plate 161 and can comprise one or a plurality of trapping electrodes for detecting electrons 204 multiplied in the microchannel plate 161.

A configuration which is symmetrical thereto is provided for the second microchannel plate 162 and the second detection device 172. The second microchannel plate 162 is arranged in the region of the front side 122 of the scintillator 120 or opposite the front side 122. Moreover, the other two electrodes 141, 142 are arranged on the front side of the microchannel plate 162. In this case, a construction comparable with FIG. 4 can likewise be present, that is to say that the electrodes 141, 142 can comprise a surface profile comparable with the electrode 150 and openings exposing channels of the microchannel plate 162. Furthermore, the scintillator 120 and the microchannel plate 162 can directly adjoin one another, wherein the microchannel plate 162 can likewise comprise, for example, one or a plurality of projecting supporting structures. The detection device 172 provided on the rear side of the microchannel plate 162 can (contrary to the illustration in FIG. 9) be directly connected to the microchannel plate 162 and can comprise one or a plurality of trapping electrodes for detecting electrons 204 multiplied in the microchannel plate 162.

During the operation of the detector element 104, the front side 122 of the scintillator 120 can face the high-energy radiation to be detected, wherein the radiation can transmit through the detection device 172 and the microchannel plate 162 and subsequently be incident in the scintillator 120. The scintillation radiation generated owing to an interaction can be converted into electrons 204 at the lateral walls 123 of the scintillator by means of the photocathode sections 130 a, 130 b, 130 c, 130 d, said electrons being accelerated in different directions and to different electrodes 142 or 151 depending on the respectively emitting photocathode section 130 a, 130 b, 130 c, 130 d, in the manner described above with reference to FIGS. 7, 8. The electrons 204 impinging on the electrodes 142, 151 can liberate further electrons 204. The electrons 204 are furthermore multiplied in the associated microchannel plates 161, 162 and detected by the associated detection devices 171, 172.

In this case, electrons 204 generated by the photocathode sections 130 a, 130 d are accelerated by means of the electrodes 141, 151 to the lower microchannel plate 161, are multiplied here and detected by the detection device 171. By contrast, the electrons 204 generated by the photocathode sections 130 b, 130 c are accelerated by means of the electrodes 152, 142 to the upper microchannel plate 162, are multiplied here and detected by the detection device 172.

The detection of electrons 204 or electron avalanches in different directions affords the possibility of determining the height or depth (“Z-position”) of an interaction of a radiation quantum 200 that excites the scintillator 120. In this case, it is possible to make use of the fact that the point in time or the temporal development and/or the magnitude of the quantities of charge detected via the detection devices 171, 172 are/is dependent on the proximity of the interaction to the front or rear side 122, 121 of the scintillator 120. In this case, too, it is possible to form corresponding summation and/or difference signals from individual measurement signals obtained by means of the detection devices 171, 172.

As described above, all the electrodes 141, 142, 151, 152 of the detector element 104 can comprise a structured surface profile and openings for exposing channels of the respective microchannel plates 161, 162. This affords the possibility that the electrodes of the two electrode pairs 141, 142 and 151, 152 can optionally be used either as cathode or as dynode (to which electrons 204 are accelerated). By way of example, provision can also be made, contrary to the illustration in FIGS. 7 and 9, for using the electrode pair 141, 151 to generate an electric field E directed upward in the direction of the microchannel plate 162, and using the electrode pair 142, 152 to generate an electric field E directed downward in the direction of the microchannel plate 161, which can be determined depending on the voltage respectively applied to the electrode pairs 141, 151 and 142, 152. Moreover, consideration can be given, if appropriate, to multiplying and detecting electrons 204 only in one direction, wherein “unidirectional” electric fields E are generated by the electrode pairs 141, 151 and 142, 152. In the case of a function as dynode, the electrons 204 accelerated to the relevant electrode can impinge thereon and liberate further electrons 204, wherein the electrons 204 can subsequently enter into the channels of the respective microchannel plates 161, 162 via the openings and can be multiplied.

Instead of such a flexible manner of operation, a fixedly predefined function as cathode and dynode can also be provided for the electrode pairs 141, 151 and 142, 152. In this case, an electrode operated as cathode does not require a structured surface, nor any openings, since no electrons 204 are accelerated to such an electrode either. Moreover, it is not necessary for a microchannel plate to be provided with channels in the region of such an electrode. With regard to such a fixedly predefined manner of operation of the electrode pairs 141, 151 and 142, 152, therefore, in a departure from the above description, provision can be made for an electrode operated as cathode not to comprise a surface profile nor to comprise openings, and thus for an associated microchannel plate also to comprise no channels, if appropriate, in this region. In this case, the electrode operated as cathode can be present as a planar continuous layer.

With regard to the detector element 104 from FIG. 9, the possibility is furthermore afforded that, in a manner comparable with the detector element 102, a further (optional) photocathode layer is provided on one of the end faces 121, 122 of the scintillator 120. It is also possible to coat, if appropriate, both end faces 121, 122 (partly) with a photocathode. In configurations of this type, the detector element 104 can comprise a corresponding electrode arrangement with the aid of which the electrons 204 emitted at the end face or at the end faces 121, 122 can also be accelerated in the direction of the associated microchannel plate 161 or 162. For this purpose, the electrode arrangement having the electrodes 141, 142, 151, 152 as shown in FIGS. 7 to 9 can be modified in such a way that corresponding electrodes or electrode layers are also arranged in the regions enclosed in a frame-shaped manner by the electrodes 141, 142 and the electrodes 151, 152. Such electrodes can also be arranged on the microchannel plates 161, 162 and comprise (if appropriate) a surface profile and openings.

Instead of embodying a detector element with only a single scintillator 120, modular configurations of detector elements comprising a plurality of scintillators 120 arranged alongside one another are also possible, which can be constructed in accordance with the approaches demonstrated above. Possible exemplary embodiments which can be realized cost-effectively, if appropriate, and which are based on the detector elements 102, 103, 104 described above are described in greater detail below. In this case, it is pointed out that with regard to details concerning aspects and components of the same type or corresponding aspects and components, reference is made to the above explanations concerning the detector elements 102, 103, 104.

FIG. 10 shows a schematic perspective illustration of a further detector element 105, which is constructed in a manner comparable with the detector element 102 from FIG. 3 and comprises three scintillators 120 arranged alongside one another. The parallelepipedal scintillators 120 are provided with photocathode sections 130 on (all) lateral walls 123. A further photocathode coating on the rear sides 121 of the scintillators 120 is also possible.

A plate-shaped electrode 140 used as cathode is arranged in the region of the front sides 122 or on the front sides 122 of the scintillators 120 and extends laterally beyond the edges thereof. Another electrode 150 is arranged on a microchannel plate 161 assigned to the three scintillators 120, wherein the microchannel plate 161 is arranged in the region of the rear sides 121 of the scintillators 120 or opposite the rear sides 121. The electrode 150 and the microchannel plate 161 extend laterally beyond the edges of the rear sides 121 of the scintillators 120. The microchannel plate 161 and the electrode 150 can have a configuration corresponding to FIG. 4, such that with regard to further details reference is made to the explanations above. This applies in the same way also to a detection device 171 arranged on the microchannel plate 161.

By means of the electrodes 140, 150, it is possible once again to generate an electric field E parallel to the longitudinal axes of the scintillators 120, whereby electrons 204 generated photoelectrically at the lateral walls 123 of the scintillators can be accelerated to the electrode 150. Electrons 204 emitted (if appropriate) at the rear sides 121 can also be accelerated to the electrode 150. Here the electrons 204 can once again eject further electrons 204 from the electrode 150, be multiplied (further) in the microchannel plate 161 and be detected by the detection device 171.

A movement of electrons also takes place in the gaps between the individual scintillators 120. For elucidation, FIG. 11 shows a schematic lateral illustration of the three scintillators 120 arranged alongside one another in the detector element 105 from FIG. 10. The scintillators 120 can be arranged relatively near to one another, as a result of which a loss in the form of radiation quanta 200 that move between the scintillators 120 and therefore do not interact with the scintillators 120 can be (largely) avoided. By way of example, relatively small distances in the range of a few 10 μm to a few 100 μm between the scintillators 120 are possible. As is indicated in FIG. 11, the electrons 204 generated by means of the photocathode sections 130 at the lateral walls 123, in the gaps between the scintillators 120, can (likewise) be accelerated to the electrode 150 or to the microchannel plate 161.

With regard to the detector element 105, the possibility is afforded that all electrons 204 that are generated photoelectrically by and come from the scintillators 120 and are multiplied in the microchannel plate 161 are detected jointly by the detection device 171. Alternatively, it is also possible for electrons 204 that come from the individual scintillators 120 and are multiplied to be detected independently of one another or separately from one another. For this purpose, the detection device 171 can have electrode regions assigned to the individual scintillators 120.

Furthermore, the possibility is afforded of designing the detector element 105 or the detection device 171 thereof in a manner comparable with the detector element 103 for separately detecting electrons 204 that are generated by different photocathodes 130 or at different lateral walls 123 of a scintillator 120 and are multiplied, such that in this case, too, it is possible to determine a lateral interaction location in a scintillator 120. For this purpose, the detection device 171 can be provided with a plurality of electrode regions or segments per scintillator 120, which are assigned to the individual photocathode sections 130 of the scintillators 120.

In the case of a modular configuration of a detector element comprising a plurality of scintillators 120, consideration can also be given to bringing about electron movements in different directions. For exemplary elucidation, FIG. 12 illustrates, in a schematic perspective illustration, a further detector element 106 comprising three scintillators 120 arranged alongside one another, which detector element is constructed in a manner comparable with the detector element 104 from FIG. 9. The detector element 106 therefore once again comprises an electrode arrangement comprising electrodes 145, 155 arranged one above another or situated opposite one another, wherein the electrodes 155 are provided on the front side of a first microchannel plate 161, and the other electrodes 145 are provided on the front side of a second microchannel plate 162. The first microchannel plate 161 is arranged in the region of the rear sides 121 and the second microchannel plate 162 is arranged in the region of the front sides 122 of the scintillators 120. A first detection device 171 is assigned to the first microchannel plate 161, and a second detection device 172 is assigned to the second microchannel plate 162.

By means of the electrodes 145, 155 situated opposite one another in pairs, which are embodied partly as L-shaped and partly as T-shaped and which are arranged on different lateral walls 123 or photocathode sections 130 of the scintillators 120, it is once again possible to produce electric fields E in different directions or mutually opposite directions. In this way, electrons 204 emitted at different lateral walls 123 of the scintillators 120 can once again be accelerated in different directions, and thus either to the first or to the second microchannel plate 161, 162. The electrons 204 multiplied here can be detected by the respective detection devices 171, 172, as a result of which, on the basis thereof, it is possible to determine a depth or height of interactions in the scintillators 120.

The embodiments explained with reference to the figures constitute preferred or exemplary embodiments of the invention. Alongside the embodiments described and depicted, further embodiments are conceivable which can comprise further modifications and/or combinations of features described. Moreover, the detectors or detector elements explained with reference to the figures can also comprise further structures (not illustrated) alongside the structures shown and described. One possible example is a connection structure which is connected to one or more photocathode sections in order to “compensate” again for the photoelectric emission of electrons by charging the photocathode section or the plurality of photocathode sections. Furthermore, it is possible to use different materials than those indicated above for a detector element or the components thereof. With regard to alternative materials, instead of a semiconductor material or instead of silicon, for example, consideration can be given to a glass material (as basic material) for a microchannel plate.

Moreover, a detector element or the components thereof can have different dimensions than those indicated above, and a detector element or the components thereof can be embodied with other geometries which deviate from the exemplary embodiments shown in the figures. Other geometries can be considered for example for electrode arrangements, in particular for electrode arrangements for bringing about electron movements in opposite directions.

Furthermore, a scintillator 120 can have, instead of a parallelepipedal shape, a different shape having two mutually opposite end faces and a (at least one) lateral wall between the end faces, wherein the end faces are connected to one another via the lateral wall, and a photocathode section can be provided on the lateral wall. One possible example is a scintillator having a cylindrical or circular-cylindrical shape. In this case, a photocathode section can be provided on a lateral wall (lateral surface) between the end faces of the scintillator, which section can in particular completely enclose the scintillator in order to efficiently convert scintillation radiation emitted to the lateral wall into electrons.

With regard to a scintillator having two mutually opposite end faces and a plurality of lateral walls situated therebetween, provision can furthermore be made for arranging a photocathode section only on one individual lateral wall or photocathode sections only on a portion of the lateral walls, such that one or more lateral walls are uncoated. It is also possible, in the case of a scintillator having one or a plurality of lateral walls arranged between two end faces, for one or a plurality of lateral walls to be provided with a photocathode section only in a partial region, rather than completely. Provision can also be made for forming photocathode sections only on lateral walls of scintillators, and for leaving the end faces of the scintillators uncoated.

In configurations of this type, a microchannel plate can be embodied in such a way that microchannels are present only in those partial regions to which electrons to be multiplied are actually moved. In a corresponding manner, an electrode which is arranged on a microchannel plate and functions as a dynode and to which photoelectrons are accelerated can be formed only in a partial region on the relevant microchannel plate (or the front side thereof). In a manner comparable therewith, a detection device can comprise one or a plurality of trapping electrodes only in a (partial) region in which channels or channels utilized for electron multiplication in an associated microchannel plate are present.

In the case also of such geometries, configurations and coatings of a scintillator, the approaches indicated above can be considered in an analogous manner in order, for example, to separately multiply and detect electrons generated by different photocathode sections or by different subsections of a photocathode section, and, if appropriate, to deflect or accelerate them in different directions, etc.

In the case of a modular configuration of a detector element, instead of three scintillators 120 arranged alongside one another (see FIGS. 10, 12), other numbers of scintillators 120 arranged alongside one another can also be provided. In this case, there is furthermore the possibility of the scintillators 120 being arranged alongside one another for example in a matrix-type fashion in the form of rows and columns. In this case, the parallelepipedal configuration of the scintillators 120 as shown in the figures proves to be advantageous for arranging the scintillators 120 alongside one another relatively closely and with small gaps.

Although the invention has been described and illustrated more specifically in detail by means of preferred exemplary embodiments, the invention is nevertheless not restricted by the examples disclosed and other variations can be derived therefrom by a person skilled in the art, without departing from the scope of protection of the invention. 

1. A radiation detector (100; 101; 102; 103; 104; 105; 106), comprising: a scintillator (120) for generating electromagnetic radiation (202) in response to the action of incident radiation (200), wherein the scintillator (120) has two mutually opposite end faces (121; 122) and a lateral wall (123) between the end faces (121; 122); a photocathode section (130) arranged on the lateral wall (123) of the scintillator (120) and serving for generating electrons (204) in response to the action of the electromagnetic radiation (202) generated by the scintillator (120); a microchannel plate (161; 162) having a plurality of channels (165) for multiplying the electrons (204) generated by the photocathode section (130); and a detection device (171; 172) for detecting the electrons multiplied by the microchannel plate (161; 162), wherein the scintillator is configured in a parallelpipedal fashion and has four lateral walls between the end faces, and wherein a photocathode section for generating electrons is arranged on each of the four lateral walls of the scintillator.
 2. (canceled)
 3. The radiation detector as claimed in claim 1, wherein a further photocathode section (131) for generating electrons (204) is arranged on an end face (121) of the scintillator (120).
 4. The radiation detector as claimed in claim 1, further comprising an electrode arrangement (140; 141; 142; 145; 150; 151; 152; 155) for bringing about a movement of generated electrons (204) to the microchannel plate (161; 162).
 5. The radiation detector as claimed in claim 4, wherein the electrode arrangement comprises a first electrode (140), which is arranged in the region of an end face (122) of the scintillator (120), and a second electrode (150), which is arranged on the microchannel plate (161).
 6. The radiation detector as claimed in claim 5, wherein the second electrode (150) is embodied in the form of a structured layer and has openings (159) via which channels (165) of the microchannel plate (161) are exposed.
 7. The radiation detector as claimed in claim 1, wherein the microchannel plate (161) is designed for multiplying electrons (204) generated by means of different photocathode sections (130).
 8. The radiation detector as claimed in claim 1, wherein the detection device (171) is designed for separately detecting electrons (204) generated and multiplied by means of different photocathode sections (130).
 9. The radiation detector as claimed in claim 1, wherein the scintillator (120), the microchannel plate (161; 162) and the detection device (171; 172) are arranged one above another.
 10. The radiation detector as claimed in claim 1, comprising: a first and a second photocathode section (130 a-130 d) arranged on a lateral wall (123) of the scintillator (120) and serving for generating electrons (204); a first and a second microchannel plate (161; 162) for multiplying electrons (204); an electrode arrangement (141; 142; 151; 152) designed to bring about a movement of electrons (204) generated by means of the first photocathode section (130 a; 130 d) to the first microchannel plate (161) and electrons (204) generated by means of the second photocathode section (130 b; 130 d) to the second microchannel plate (162); a first detection device (171) for detecting electrons (204) multiplied by the first microchannel plate (161); and a second detection device (172) for detecting electrons (204) multiplied by the second microchannel plate (162).
 11. The radiation detector as claimed in claim 1, comprising: a number of a plurality of scintillators (120) which are arranged alongside one another and on the lateral walls (123) of which are arranged photocathode sections (130) for generating electrons (204); a microchannel plate (161; 162) for multiplying electrons (204) generated by means of photocathode sections (130) of the plurality of scintillators (120); and a detection device (171; 172) for detecting the electrons (204) multiplied by the microchannel plate (161; 162).
 12. An imaging system (110), comprising: a radiation detector comprising: a scintillator for generating electromagnetic radiation in response to the action of incident radiation, wherein the scintillator has two mutually opposite end faces and a lateral wall between the end faces; photocathode section arranged on the lateral wall of the scintillator and serving for generating electrons in response to the action of the electromagnetic radiation generated by the scintillator; a microchannel plate having a plurality of channels for multiplying the electrons generated by the photocathode section; and a detection device for detecting the electrons multiplied by the microchannel plate, wherein the scintillator is configured in a parallelpipedal fashion and has four lateral walls between the end faces, and wherein a photocathode section for generating electrons is arranged on each of the four lateral walls of the scintillator. 